The technical field of the invention is that of devices for connecting and separating objects such as microsatellites with respect to a structure. More generally, the items concerned are devices for the placement of satellites from a rocket, the purpose of which is to unlock the satellite from its support and move it rapidly away therefrom by ejection.
In this patent application, the concepts of xe2x80x9cseparation nutxe2x80x9d, xe2x80x9cunlockingxe2x80x9d and xe2x80x9cunlocking devicexe2x80x9d are equivalent.
More specifically, the invention relates to a separation nut intended to release a screw which holds two subassemblies of a structure together, this release taking place through the movement of a release ring by virtue of the gases produced by a gas generator.
The particularity of the invention lies in the fact that the triggering of the unlocking device makes it possible, in a preliminary phase, to create a damping device intended to decelerate then gently halt the release ring just before it strikes a shutter. Thus, by avoiding a sharp mechanical shock, the equipment items secured to the structure connected to the separation nut are spared, thus ensuring clean and gentle separation of the two subassemblies. Now, as this separation has to occur very quickly, it would not be appropriate to try to slow down the mechanism by which the device works in order to get around this mechanical shock problem. Only the intervention of an appropriate damping device makes it possible to avoid any disruption due to a mechanical shock, while keeping the unlocking device operating extremely well.
Damping devices included in devices for unlocking two subassemblies already exist and have been covered by numerous patents. Mention may in particular be made of Patent FR 2 736 615 which relates to a split-nut unlocker for a microsatellite and of which the principle of operation, involving the sliding of various mechanical components such as, in particular, a release ring around a nut, is also well known. With a view to dissipating the shock upon impact of certain components, a solid damper is fixed to one of the ends of the device. A single figure of the device thus described reveals a significant bulk due to the presence of this solid damper.
U.S. Pat. No. 3,926,090 for its part describes a separation nut which also works on the principle of the sliding of various components. Damping is achieved by means of a chamber filled with air at ambient pressure, the said chamber being shuttered by a moving part. As the nut is triggered, the moving part tends to move sharply in the chamber. The air thus trapped becomes compressed under the effect of the diminishing volume, ending up forming a compressible pneumatic sausage that prevents the part from striking the end of the chamber. Such a damping system has the drawback of not being very reliable in so far as it is dependent on the chamber being sealed correctly, something which is difficult to achieve under such conditions. In addition, since the chamber is pressurized after the part has moved, the damping system has only a very small influence on the start of the travel of the part and has therefore to put up a great deal of resistance, this being even more unpredictable to master.
Finally, U.S. Pat. No. 4,187,759 relates to a separation nut, the principle of operation of which relies on the combined effect of movement of the release ring to release a split nut and thrust from an ejector to expel the connecting screw initially engaged in the nut. A spring is placed in the device to allow the release ring to return to its initial position and thus allow the separation nut to be reused. Although this is not specified in the patent, the said spring, by becoming compressed under the effect of the moving release ring, seems also to exert a function of decelerating the said ring. However, such a deceleration system is not very satisfactory in terms of damping in so far as the release ring, moving very fast over a very short space of time, sharply compresses the spring until its coils come into contact with one another, this act of becoming coil bound itself giving rise to a shock. Thus, while the spring can slightly attenuate the shock generated by the release ring, it is not capable, by itself, of ensuring that the shock is completely eliminated.
The unlocking device according to the invention, which works by the sliding of a release ring around a nut, has a pneumatic device for damping the said ring that makes it possible to get around all the aforementioned problems raised by the state of the art. This is actually achieved by simple influx of gas into a space belonging to the said unlocking device. It therefore does not involve any additional solid component specially designed for this damping function, thus avoiding needless additional load and bulk. In addition, as the influx of gas to the space occurs just before the ring moves or, at the latest, at the same time, the damping function occurs right from the start of the travel of the said ring, thus decelerating its movement right from the start and preventing this ring from acquiring too much kinetic energy which would always lead to an appreciable mechanical shock. Finally, regardless of the characteristics of the unlocking device used, it is always possible to adjust the xe2x80x9cenergy reserve/space volumexe2x80x9d pairing so as to obtain total damping of the ring under all circumstances. To finish off with, the damping device included in the unlocking devices according to the invention maintains full effectiveness regardless of the temperature of the environment, unlike, for example, certain solid damping devices such as those employing elastomers which are ineffective at low temperature.
The subject of the present invention is concerned with a device for unlocking two subassemblies, comprising a body, a gas generator, a gas expansion chamber, a release ring, an ejector, a segmented nut, a connecting screw and a shutter, initiation of the gas generator causing the release of the gases in order, on the one hand, to cause the release ring to slide in such a way so as to release the segments of the nut and, on the other hand, bring the ejector up to speed so that it drives the connecting screw and ejects it from said nut, characterized in that a damping device achieved by the influx of a compressible fluid into a space of the unlocking device is created by the release of the gases, said damping device being intended to decelerate then halt the release ring before it reaches the shutter.
In order to be fully effective, the space needs to become filled with compressible fluid just before the release ring begins to move so that the pneumatic sausage can act right from the start of the said movement. One of the essential features of the damping device is that it does not exist when the unlocking device is not activated and that it does not come into operation until it will be of use to the said unlocking device. Advantageously, the gas generator is a pyrotechnic gas generator comprising a pyrotechnic charge and an initiation device. As a preference, the initiation device comprises an electropyrotechnic system. Advantageously, the damping device is achieved by pressurizing the space with gas. This is because, since the invasion of the space has to constitute an extremely short sequence in the overall unlocking process, a fluid in the form of a gas would seem to be a particularly appropriate solution.
As a preference, the space is pressurized by tapping gas from the expansion chamber using a connecting system that places the space in communication with said chamber. Thus, the source of energy of the unlocking device, which takes on the form of a gas generator, has the twofold function of operating the unlocking device and at the same time of creating a device for damping the release ring, so as to ensure separation of the two subassemblies without appreciable mechanical shock.
Advantageously, the release ring has a widened base, one face of which is in contact with the expansion chamber, and the space is an annular space located around the said ring and in the continuation of the said base, the connecting system being represented by an annular passage located between the body of the unlocking device and the external lateral surface of the widened base. Indeed it is desirable for the space to be near the expansion chamber so that the connecting system can be shortened and simplified and so as to allow it to be pressurized quickly. In addition, the said space needs to be integrated into the unlocking device without creating any additional volume liable to influence the overall size of the said device.
According to another embodiment of the invention, the widened base isolates the space from the expansion chamber and the connecting system comprises at least one duct passing through the said widened base to cause the said space to communicate with the said chamber. As a preference, the unlocking device comprises a return device allowing the ring which has moved during operation to return to its initial position when the gas generator is no longer producing gas.
In this way, the unlocking device returns to its pre-operating starting configuration, and can thus be reused as it is without any modification. By this means, the unlocking device according to the invention can be tested once initially on the ground before being used in the actual configuration, in particular, on a rocket or on a missile if the test proves conclusive.
As a preference, the ejector is in the form of a cylindrical body, one end of which ends in a widened head opening into the expansion chamber and the other end of which rests against the connecting screw.
Advantageously, the ejector is housed in a separator that can be likened to an approximately cylindrical component, one end of which emerges in the expansion chamber, and the other end of which ends in a widened head resting against the nut.
Advantageously, the return device consists of a spring resting both against the widened head of the separator and the widened base of the release ring.
The way in which these components are arranged with respect to each other and their particular geometry have the sole purpose of contributing to the release of the segmented nut while at the same time pressing on the connecting screw to expel it. What happens is that the gases emitted by the gas generator will simultaneously push the separator at its end emerging in the expansion chamber and the ejector at its widened head. The thrust on the separator has the result of tending to open the nut via the widened head of the said separator, and the thrust exerted on the widened head of the ejector leads it to move in the separator with the result that the connecting screw against which it rests is expelled.
As a preference, the release ring and the nut each comprise at least two annular bulges, the cross sections of which exhibit sloping lines allowing these two components which, at rest, are in contact at their respective bulges, to slide one with respect to the other under the effect of the gases emitted, and then later to return to their position of rest.
The unlocking devices according to the invention involving a damping device for the release ring have the advantage of being economical and not very bulky. They are not very bulky in so far as the damping device does not exist for as long as the unlocking device is not triggered and is created in the form of an influx of gas that does not entail the participation of additional solid components especially designed for this damping function. They are economical because the damping device taps into a source of energy that already exists and does not need to be integrated into a parallel and self-contained fluid circuit with its own source of energy.
Finally, the damping device employed in the unlocking devices according to the invention has the advantage of maintaining its damping ability regardless of the temperature of the surroundings in which separation of the two subassemblies is to occur, unlike certain solid damping devices such as those using elastomers which are ineffective at low temperature.